This is unreleased documentation for SUSE® Storage 1.12 (Dev).

Kubelet Volume Metrics

About Kubelet Volume Metrics

Kubelet exposes the following metrics:

  1. kubelet_volume_stats_capacity_bytes

  2. kubelet_volume_stats_available_bytes

  3. kubelet_volume_stats_used_bytes

  4. kubelet_volume_stats_inodes

  5. kubelet_volume_stats_inodes_free

  6. kubelet_volume_stats_inodes_used

Those metrics measure information related to the file system of a PVC inside a Longhorn block device.

They are different than longhorn_volume_* metrics, which measure information specific to a Longhorn block device.

You can set up a monitoring system that scrapes Kubelet metric endpoints to obtains a status of PVC and set up alerts for abnormal events, such as the PVC being about to run out of storage space.

A popular monitoring setup is prometheus-operator/kube-prometheus-stack, which scrapes kubelet_volume_stats_* metrics and provides a dashboard and alert rules for them.

Longhorn CSI Plug-in Support

Longhorn CSI plug-in supports the NodeGetVolumeStats RPC according to the CSI spec.

This allows the kubelet to query the Longhorn CSI plug-in for status of PVC.

The kubelet then exposes that information in kubelet_volume_stats_* metrics.